The number of patients to include was baszd on the hypothesis that intubation rate would be reduced from 40 with HME to 25% with HME. A total of 250 patients was required with alpha risk of 0,05 and beta risk of 0,2 (power 80%). Intubation criteria were predefined according to the litterature. The expected duration was 18 months. The official support was institutional (DRRC of AP-HP). HH were furnished free of charge, as well as HME. Masks used were the same in both groups.